Environmental Impacts of Acid Deposition (College Board AP® Environmental Science): Study Guide

Distribution of acid deposition

• Acid deposition is not confined to the immediate vicinity of emission sources

• Acid deposition is more likely to affect locations downwind of big industrial regions because winds can carry particulate debris from dry deposition

• Wet deposition occurs at a distance from the source

• Transboundary pollution can occur in countries other than the source

• Acid rain affects both the living and the non-living

Acidification by acid rain and deposition

• Acid deposition can react with metals and rocks (such as limestone), damaging buildings and statues

• Removing a whole tree can be equivalent to the effect of 60 years of acid rain

Structures

• Limestone and marble both contain calcium carbonate (CaCO₃)

• The calcium carbonate reacts with sulfuric acid or nitric acid, causing stonework to corrode and weaken

Water

• Acidic deposition, particularly in bodies of water, directly affects aquatic organisms such as fish, amphibians, and invertebrates

• When acid rain falls on bodies of water, pH levels fall and cannot support life

• Further decreases in pH levels release nitrates and aluminium from rocks

• High levels of aluminum ions become toxic to fish, affecting their respiratory systems, impairing growth, and even causing death

• Acid rain can leach copper, aluminum, and other heavy metals out of the soil and into runoff and drinking water

Soil and plants

• Acid rain directly contaminates soils

• The contaminated precipitation infiltrates and percolates into the horizons of the soil and lowers the pH

• This dissolves essential minerals and nutrients from the soil that plants need to grow

• Toxic metals like aluminum are leached from the soil and are harmful to plants and animals

• Acid rain has a negative impact on forests and trees as sulfur dioxide interferes with the process of photosynthesis

• Acid deposition directly falls on leaves, causes leaf damage and eventually kills plants

• Acid particulates can block stomata (plant pores), preventing gaseous exchange

• Acid deposition is especially harmful to coniferous forests such as pine and spruce due to their shallow root systems and thin bark

  • Acid rain also damages foliage and hinders nutrient absorption

Regional differences in acid deposition impacts

• Differences in soil thickness, composition and bedrock type affect the impact that acid deposition has on a region

• Areas that have naturally occurring calcium or limestone deposits are able to neutralize some of the acids and therefore reduce the effects of acid deposition

• Areas with large numbers of trees and other vegetation absorb CO₂ from the air and can help neutralize the effects of acid rain

• Episodic acidification can occur with seasonal snow melt and strong rain

• Acid rain can briefly affect lakes with low acidity when melting snow or rain brings more acidic deposits and the soil can not neutralize it

• This short-term increase in acidity (lower pH) can stress the environment and harm or kill many organisms

• Acidic fog and clouds at higher altitudes may deplete tree nutrients, leaving them weaker and less able to survive freezing conditions